This section of the Dog Law of 1919 provides that any dog over six months must be registered and wear a collar at all times. It also mandates that female dogs in heat must be kept on their owners' premises or restrained on a leash. The overall leash requirement is less clear, stating that it is unlawful for an owner to allow a dog "
to stray unless held properly in leash." This does appear to mandate a statewide leash requirement for dogs, however.

Statute Text:

Sec. 2. It shall be unlawful for any person to own any dog 6 months old or over, unless the dog is licensed as hereinafter provided, or to own any dog 6 months old or over that does not at all times wear a collar with a tag approved by the director of agriculture, attached as hereinafter provided, except when engaged in lawful hunting accompanied by its owner or custodian; or for any owner of any female dog to permit the female dog to go beyond the premises of such owner when she is in heat, unless the female dog is held properly in leash; or for any person except the owner or authorized agent, to remove any license tag from a dog; or for any owner to allow any dog, except working dogs such as leader dogs, guard dogs, farm dogs, hunting dogs, and other such dogs, when accompanied by their owner or his authorized agent, while actively engaged in activities for which such dogs are trained, to stray unless held properly in leash.